Equity Incentive Plans (Tables)

6 Months Ended

Jun. 30, 2021

Stock-based Compensation

Assumptions used in the black-Scholes model

The assumptions used in the Black-Scholes model are presented below:

	Six months ended
	June 30, 2021	June 30, 2020
Risk-free interest rate	0.90% --1.29%	0.46% -- 1.51%
Expected volatility	93.37%	90.43%
Expected term (in years)	5.50 - 7.00	5.75 - 6.25
Expected dividend yield	0%	0%

Allocation of Stock-Based Compensation Expenses

The tables below summarize the total stock-based compensation expense included in the Company’s consolidated statements of operations for the periods presented:

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Research and development	$	399,000	$	299,000	$	752,000	$	636,000
General and administrative		508,000		607,000		997,000		1,314,000
Total stock-based compensation	$	907,000	$	906,000	$	1,749,000	$	1,950,000

Summary of Stock Option Activity

Stock option transactions during the six months ended June 30, 2021 are presented below:

	Options Outstanding
				Weighted
				Average
		Weighted		Remaining
		Average		Contractual	Aggregate
		Exercise		Term	Intrinsic
	Shares	Price		(Years)	Value
Outstanding at December 31, 2020	1,668,926	$	6.30	8.32		—
Granted	719,750		4.96			—
Exercised	(46,134)		3.34		$	82,000
Forfeited/Cancelled	(7,474)		71.89	—		—
Outstanding at June 30, 2021	2,335,068	$	5.73	8.25	$	1,115,000
Vested and expected to vest at June 30, 2021	2,335,068	$	5.73	8.25	$	1,115,000
Exercisable at June 30, 2021	744,996	$	9.41	6.50	$	466,000

Schedule of restricted stock awards

Restricted stock awards during the six months ended June 30, 2021 are presented below:

		Weighted Avg
		Grant Date
	Shares	Fair Value
Outstanding at December 31, 2020	322,756	$	19.55
Granted	—		—
Forfeited/Cancelled	(924)		4.46
Vested and Issued as Common Stock	(167,691)		12.33
Outstanding at June 30, 2021	154,141	$	27.49

Shares Reserved for Future Issuance

As of June 30, 2021, the Company had reserved shares of its common stock for future issuance as follows:

	Shares Reserved
Stock options outstanding	2,335,068
Unvested restricted stock units	30,000
Employee stock purchase plan	9,748
Available for future grants under the 2016 Plan	359,822
Warrants outstanding	16,647,219
Total shares reserved	19,381,857